The new version of MediaWiki will be on test wikis and MediaWiki.org from 4 October. It will be on non-Wikipedia wikis and some Wikipedias from 5 October. It will be on all wikis from 6 October (calendar).
Talk pages on the mobile site will change at the Arabic, Bangla, Chinese, French, Haitian Creole, Hebrew, Korean, and Vietnamese Wikipedias. They should be easier to use and provide more information. (Last week's release was delayed)
The scribunto-console API module will require a CSRF token. This module is documented as internal and use of it is not supported. 
The Vector 2022 skin will become the default across the smallest Wikimedia projects. Learn more.